The present invention relates to an onboard aircraft flight path optimization system. More particularly, the present invention relates to an onboard aircraft flight path optimization system that includes an onboard performance management system computer, an onboard pilot keyboard for inputting the coordinates of a remote position, an onboard weather radar for determining the wind at the remote position, an onboard inertial navigation system for determining the local wind, an onboard infrared probe for determining the temperature at the remote position, and an onboard temperature probe for determining the local temperature wherein the onboard performance management system computer constantly compares the remote position wind with the local wind and constantly compares the remote position temperature with the local temperature so as to provide the most economical flight path to a destination.
Turbulence is any motion of the air other than large-scale motion. Large-scale motions are primarily horizontal and are depicted on an aircraft's constant-pressure charts. The contours or stream lines show the direction, and the isotachs the speed, of large-scale motions.
Departures from large-scale movement are called turbulence, and they may be vertical or horizontal. Turbulence first appears as large eddies. Sometimes ten miles or more in diameter, these eddies tend to break down and become progressively smaller. "Eddy" usually infers circular motion but includes all turbulent motion.
Frequently the terms "draft" and "gust" are associated with turbulence, drafts with large eddies and gusts with small eddies, but there is no distinct differences between the two. For eddies of intermediate size, the effects on an aircraft is a combination of vertical displacements (drafts) and bumpiness (gusts).
Convection is a cause of turbulence and an aircraft must adjust its operational factors accordingly.
Convective turbulence is associated with thermal instability and can be expected whenever the existing temperature lapse rate approaches the value for the dry adiabatic lapse rate (3 degrees per 1000 ft.). When unstable conditions occur in the atmosphere, any vertical motion (upward or downward) initiated in the unstable layer will continue and tend to be accelerated until it reaches the top or bottom of the layer.
The momentum of the moving air parcel carries it through the upper or lower boundary of the unstable layer, where the motion will be damped out. Vertical mixing continues through the layer, establishing an adiabatic lapse rate.
A thunderstorm provides an ideal mechanism for the development of severe to extreme convective-type turbulence. If there is a deep layer of unstable air and if sufficient lifting is available or radiational cooling aloft occurs, thunderstorms can be expected to develop.
Many synoptic conditions are known to produce thunderstorm activity including frontal, orographic, air mass, gust fronts, and microburts.
When a typical cold front moves into an area of relatively deep, moist, and unstable air, the necessary mechanical lifting is present to generate thunderstorm activity.
Rough terrain provides mechanical lifting to air that is flowing perpendicular to the terrain, and if the air is unstable and moist, thunderstorms may occur.
Air-mass thunderstorms are produced by heating over land areas, horizontal convergence (not associated with a frontal system), or radiational cooling aloft.
The strong winds and low-level wind shears that precede thunderstorms are known as "gust fronts," "first gusts," or "plow winds." They produce wind shear events that can produce a major loss of headwind. Aircraft caught in such events can lose a substantial amount of airspeed suddenly.
Microbusts can also accompany thunderstorms. Two miles or less in diameter, microburts are violent short-lived descending columns of air capable of producing horizontal winds sometimes exceeding 60 knots within 150 feet of the ground. They produce wind shear events that can produce a major loss of headwind and major downdrafts of air. Aircraft caught in such events can lose a substantial amount of airspeed suddenly.
Other causes of severe weather conditions include tornadoes, prefrontal squall lines, tropical cyclones, the intertropical convergence zone, easterly waves, electrical discharges (lightning), mountain waves, jet streams, and fronts.
A tornado is a violently rotating column of air within, and extending from, a cumulonimbus. Tornadoes are usually observable as a funnel cloud or vortex ranging in diameter from about 100 feet to 1 mile. Tornadoes rotate cyclonically at very high speed and contain extreme turbulence and very low barometric pressure.
Tropical cyclones are characterized by an eye surrounded by a ring or wall of clouds (called wall cloud) and inward-oriented spiral bands. The greatest turbulence is found in the wall cloud. In an intense hurricane or typhoon, the wall cloud heights can reach 75,000 feet, and heights of 50,000 to 60,000 feet are common. Reports from jet hurricane reconnaissance flights indicate a considerable variation in turbulence between storms and altitudes. At times severe turbulence is encountered as high as 40,000 feet as well as at lower levels.
A prefrontal squall line is an instability line located in the warm sector of a cyclone, about 50 to 300 miles in advance of a cold front, usually oriented roughly parallel to the cold front and moving in the same manner as the cold front. However, at times squall lines develop at right angles to west-east warm or stationary fronts. Often thunderstorm activity and turbulence are more severe along a prefrontal squall line than that associated with the accompanying front to the west of the squall line.
The intertropical convergence zone, sometimes called the "Intertropical" or "Tropical Front," is a zone of convergence between the trade winds of the Northern and Southern Hemispheres or between trades of one hemisphere and the recurved trades (monsoons) of the other. The intertropical convergence zone migrates seasonally toward the summer hemisphere and lags one or two months behind the sun. Periodically waves develop along the intertropical convergence zone and move from east to west. Weather conditions along the intertropical convergence zone may create cumulonimbus clouds in a solid line that may extend from 1000 feet above the surface to more than 50,000 feet.
The easterly wave is a zone of convergence generally oriented in the NNE to SSW direction, moving from east to west in tropical regions. Easterly waves are encountered during the late spring, summer, and early fall. The easterly waves can generate cumulonimbus activity, severe squall and thunderstorm activity with associated severe turbulence over a relatively widespread area at varying altitudes. Quite often, intense easterly waves develop into hurricanes.
Electrical discharges (lightning) may occur in the atmosphere because of large variations in electrical potentials within a cloud, between adjacent clouds, or between clouds and the earth or other objects. Most intense electrical discharges are directly related to the separation of negative and positive charges by convective currents. Approximately 80 percent of observed discharges on aircraft have occurred while the aircraft were flying near the freezing level in convective-type clouds.
A mountain wave, sometimes called a "standing wave," is a disturbance in the atmosphere set up by a mountain barrier and characterized by a wave-like airflow producing strong currents and severe turbulence. The most turbulent area of a mountain wave is centered around the roll cloud at levels mainly below 20,000 feet. When jet-stream conditions are present, there is a layer of severe turbulence at the tropopause level. While the laminar flow between the lenticular clouds may consist of only moderate updrafts and downdrafts, it may break down into eddies, producing severe turbulence in the whole layer from the surface to the tropopause.
One study indicates that 85% of turbulence reported by aircraft is in some way related to jet streams. Although this includes cases classified as "light" and "moderate," and doubtless the percentage would be much lower in the "severe" category, the fact remains that jet streams are a very significant factor in the cause of severe turbulence. Jet streams cause turbulence when there are large amounts of horizontal wind shear, when there are large amounts of vertical wind shear, when a jet stream blows across a land barrier, or when two merged jet streams diverge. The effect of vertical wind shear is to produce the greatest amount of turbulence just above the core level of the jet stream where the tropopause, on the "high pressure" side of the jet stream, is close to the jet stream core. Another predominant region of turbulence is in the frontal region below the core of the jet stream. Both of these areas represent the maximum vertical wind shear. It is difficult to avoid jet stream turbulence in flight, especially in clear air, ergo "clear air turbulence."
Fronts are boundaries between air masses of different properties. Fronts on a vertical plane slope in the direction of the cold air. Although the steeper cold fronts usually produce more violent cloud activity and draft-type turbulence, the wind shears and associated gust-type turbulence may be just as great in the warm front. Very strong directional shear is present in levels below 10,000 feet in both the cold and warm frontal boundaries and cause considerable turbulence.
It is apparent that weather plays an important factor in determining turbulence. Turbulence occurs at specific altitudes and when encountered can greatly effect the operational factors of the aircraft especially in the form of fuel consumption.
Another factor influenced by altitude, is the freezing point of the fuel. The freezing point of the fuel can become a problem on long-duration high-altitude flights where fuel can freeze and cause engine starvation. On medium and long flights, the minimum fuel tank temperature does not necessarily occur at the top of descent. Enroute air masses containing temperatures well below standard values can cause the coldest tank temperatures to occur during the cruise phase. The fuel temperature must be monitored carefully to ascertain when it has dropped below a minimum temperature limit. If indications are present that the minimum temperature limits will be exceeded, then preventive action is required before the fuel temperature becomes critical. Fuel temperature can be increased, if necessary, by increasing the cruise Mach number, by reducing the altitude, or by diverting to a warmer track.
Numerous innovations for weather determining devices have been provided in the prior art that will be described. However, even though these innovations may be suitable for the specific individual purposes to which they address, they differ from the present invention in that they do not teach an onboard aircraft flight path optimization system that includes an onboard performance management system computer, an onboard pilot keyboard for inputting the coordinates of a remote position, an onboard weather radar for determining the wind at the remote position, an onboard inertial navigation system for determining the local wind, an onboard infrared probe for determining the temperature at the remote position, and an onboard temperature probe for determining the local temperature wherein the onboard performance management system computer constantly compares the remote position wind with the local wind and constantly compares the remote position temperature with the local temperature so as to provide the most economical flight path to a destination.
For example, Lebrun U.S. Pat. No. 4,281,383 teaches a process and system for the detection of a wind gradient or change for an aircraft. The system includes a first subtractor. A derivator connected to the first subtractor and generating a first subtractor signal received by a second subtractor. The second subtractor in combination with a third subtractor generates a third subtractor signal amplified by an amplifier.
Another example, Keedy U.S. Pat. No. 5,105,191 teaches an apparatus and method for detecting and indicating severe weather conditions such as wind shear and clear air turbulence. The system includes a sensor for detecting the weather parameter of air temperature differential and a computer for comparing the parameter value with a stored constant value. When the parameter value exceeds the constant value, a severe weather condition warning indication is generated by the computer as a visual and/or audio signal.
Still another example, Even-Tov U.S. Pat. No. 5,281,815 teaches a method for determining the humidity and temperature of atmospheric air at selected distances along a field of view by passive infrared spectrometry. A plurality of infrared power density values received by an infrared spectrometer along the field of view at a plurality of discrete, selected infrared wavelengths are measured.
Finally, yet another example, Barrett U.S. Pat. No. 5,285,070 teaches an apparatus for remotely sensing changes in the spatial temperature profile of a column of atmospheric air. The apparatus includes collecting means for receiving the thermal radiation from a column of atmospheric air and for directing it to intensity sensing means. Sensing means with rotatively mounted interference bandpass filter together with means for rotating the filter sequentially turns to and senses the intensity in the column of atmospheric air of at least two spatial regions in the 4.17 to 4.2 um region of the carbon dioxide spectral emission band. Means detect temporal changes in the relative intensity of the spectral regions.
It is apparent that numerous innovations for weather determining devices have been provided in the prior art that are adapted to be used. Furthermore, even though these innovations may be suitable for the specific individual purposes to which they address, they would not be suitable for the purposes of the present invention as heretofore described.